Hotmelt composition comprising three polymers having different peak molecular weights

Abstract

A hotmelt composition comprises at least three co-polymers defined by their chemistry and molecular weight. The hotmelt composition may be without tackifiers. The hotmelt can be used in absorbent articles such as diapers comprising two substrates at least partially attached by the hotmelt composition. The hotmelt provides especially good nonwoven-nonwoven bond and nonwoven-film bond.

What is claimed is: 
     
       1. A hotmelt composition comprising:
 from 30% to about 70% of a first polymer or mixture of polymers having a peak molecular weight below 40,000 g/mol; 
 from about 10% to about 70% of a second polymer or mixture of polymers having a peak molecular weight above 40,000 g/mol; and 
 from about 2% to about 20% of a third polymer or mixture of polymers having a peak molecular weight of from about 70,000 g/mol to about 700,000 g/mol, wherein the peak molecular weight of the third polymer or mixture of polymers is greater than the peak molecular weight of the second polymer or mixture of polymers by at least 10,000 g/mol. 
 
     
     
       2. The hotmelt composition according to  claim 1 , comprising by weight of the hotmelt composition:
 from about 40% to about 60% of the first polymer or mixture of polymers; 
 from about 30% to about 50% of the second polymer or mixture of polymers; and 
 from about 5% to about 15% of the third polymer or mixture of polymers. 
 
     
     
       3. An absorbent article comprising a first substrate and a second substrate, wherein the first substrate and the second substrate are at least partially bonded by the hotmelt composition according to  claim 1 , and wherein either a) the first substrate is a first nonwoven and the second substrate is a second nonwoven or b) the first substrate is a nonwoven and the second substrate is a plastic film. 
     
     
       4. A package comprising a plurality of the absorbent articles according to  claim 3 . 
     
     
       5. A process for bonding a first substrate to a second substrate, the process comprising the step of applying the hotmelt composition according to  claim 1  on the first substrate and/or the second substrate by a contact applicator and pressing the two substrates together before the hotmelt composition solidifies to create a bond between the two substrates, wherein the hotmelt composition is applied on the first substrate and/or the second substrate at a line speed of more than 2 m/s. 
     
     
       6. A hotmelt composition comprising:
 from 30% to about 70% of a first propylene-ethylene copolymer having a peak molecular weight below 40,000 g/mol; 
 from about 10% to about 70% of a second propylene-ethylene copolymer having a peak molecular weight above 40,000 g/mol; and 
 from about 2% to about 20% of a third polymer or mixture of polymers having a peak molecular weight of from about 70,000 g/mol to about 700,000 g/mol, wherein the peak molecular weight of the third polymer or mixture of polymers is greater than the peak molecular weight of the second copolymer by at least 10,000 g/mol; 
 
       wherein the peak molecular weight is measured according to the Peak Molecular Weight Measurement Method. 
     
     
       7. The hotmelt composition according to  claim 6 , wherein the first propylene-ethylene copolymer has a peak molecular weight ranging from about 4,000 g/mol to about 31,000 g/mol. 
     
     
       8. The hotmelt composition according to  claim 6 , wherein the second propylene-ethylene copolymer has a peak molecular weight ranging from about 50,000 g/mol to about 130,000 g/mol. 
     
     
       9. The hotmelt composition according to  claim 6 , wherein the third polymer or mixture of polymers is a propylene-ethylene copolymer comprising greater than 80% by weight of polypropylene units. 
     
     
       10. The hotmelt composition according to  claim 9 , wherein the third propylene-ethylene copolymer has a peak molecular weight ranging from about 130,000 g/mol to about 410,000 g/mol. 
     
     
       11. The hotmelt composition according to  claim 6 , wherein at least one selected from the first propylene-ethylene copolymer, the second propylene-ethylene copolymer, and third polymer or mixture of polymers is a metallocene-technology based propylene-ethylene copolymer. 
     
     
       12. The hotmelt composition according to  claim 6 , wherein the hotmelt composition comprises from about 0% to less than 30% by weight of a tackifier. 
     
     
       13. The hotmelt composition according to  claim 6 , wherein the second propylene-ethylene copolymer has an enthalpy of fusion of from about 25 J/g to about 45 J/g, and the first propylene-ethylene copolymer has an enthalpy of fusion of from about 5 J/g to about 15 J/g, as measured according to the Enthalpy of Fusion Test Method. 
     
     
       14. The hotmelt composition according to  claim 6 , wherein the viscosity of the hotmelt composition at 170° C. is in the range from about 1,000 mPa·s to about 7,000 mPa·s, as measured according to the Viscosity Test Method. 
     
     
       15. An absorbent article comprising a first substrate and a second substrate, wherein the first substrate and the second substrate are at least partially bonded by the hotmelt composition according to  claim 6 , and wherein either a) the first substrate is a first nonwoven and the second substrate is a second nonwoven or b) the first substrate is a nonwoven and the second substrate is a plastic film. 
     
     
       16. A package comprising a plurality of the absorbent articles according to  claim 15 . 
     
     
       17. A process for bonding a first substrate to a second substrate, the process comprising the step of applying the hotmelt composition according to  claim 6  on the first substrate and/or the second substrate by a contact applicator and pressing the two substrates together before the hotmelt composition solidifies to create a bond between the two substrates, wherein the hotmelt composition is applied on the first substrate and/or the second substrate at a line speed of more than 2 m/s.